146 



COMPARATIVE ANATOMY 



segmented off secondarily (Fig. 98) : it is perforated by nerves, 

 and gives rise on either side to an iliac process (most marked in the 



Holocephali) extend- 

 Cep 



Rr' BP 



PP 



ing upwards into the 

 lateral walls of the 

 body (Fig. 105). A 

 prepubic process is also 

 present, and there is 

 i apparently also an in- 

 dication of a median 

 epipubic process (cf. 

 infra}. The whole 

 pelvic plate essentially 

 corresponds, more or 



FIG. 105. DIAGRAM OF THE ELASMOBRANCH PELVIS, less completely, with 

 From the ventral side. 



the ischiopubis of 

 higher forms. 



In the Dipnoi, the 

 narrow cartilaginous 



Bas, Pro, Rad, basipterygium, propterygium, and 

 radii of the fin ; BP, pelvic plate (ischiopubis) ; 

 Cep, epipubic process ; Fo l , obturator foramen ; 

 /, iliac process ; PP, prepubic process ; Sy, 

 region of the ischiopubic symphysis. pelvic plate (Fig. 106) 



is provided with a long 



and delicate anterior median, a short posterior median process, 

 and two pairs of lateral processes. Of the latter the anterior 

 (prepubic processes) are much 

 longer in Protopterus than in 

 Ceratodus, and each is embedded 

 in an intermuscular septum ; 

 with the posterior process the 

 skeleton of the fin is articu- 

 lated by means of an inter- 

 mediate piece. The anterior 

 unpaired process may be looked 

 upon as an epipubic process, 

 corresponding with that of Am- 

 phibia and Amniota (q. v.*). The 

 post 



bears a ridg( 

 of muscles. 



Amphibians. It will be 



jterior or hypoischiatic process 

 irs a ridge for the attachment 



seen by a glance at Fig. 104, D, 

 & ' ' 



that the ventral portion of the 

 pelvic arch of Necturus is formed 

 on the same plan as the pelvic 

 plate of the Dipnoi and Crosso- 

 pterygii, but in all Urodela and 

 Amniota it is perforated by the 

 obturator nerve. Like the pelvis 

 of all Vertebrates, it has a paired origin, and in Proteus and 



FIG. 106. PELVIS OF -Protopteru*. From 

 the ventral side. 



a, prepubic process, which may become 

 forked at its distal end ; b, process to 

 which the pelvic fin (HE) is attached ; 

 c, epipubic process ; (fr, ridge for 

 attachment of muscles ; M, myotomes ; 

 M l , intermuscular septa. 



